Art of coating



Patented Dec. 27, 1927.

UNITED STATES PATENT OFFICE.

BENJAMIN TALBOT, OF NORTH ALLERTON, ENGLAND, ASSIGNOR TO' TALBOT NON- CORROSIVE LININGS COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORA- T1011 OF DELAWARE.

No Drawing. Application filed May 12, 1925, Serial No. 29,652, and in Great Britain April 24, 1925.

My invention is particularly designed to provide a firmly adhering bituminous coating for metallic articles and lining for metal pipe, as described in my Letters Patent of the United States No.1,555,257 and forming thereon a covering or liningof substantial thickness and glossy surface so indurated as to withstand summer or tropical heat conditions without softening or becoming viscous or sticky while retaining sufiicient flexibility or pliancy to resist cracking or flaking as a result of freezing or bending.

The tars and asphalts found in nature or as artificially produced are usually too soft in summer to retain their desired consistency and so brittle in winter that they crack or peel. By my improvements the natural properties of such bitumens are so modified that the desired toughness and hardness without brittleness are obtained and a stable coating of substantial thickness may be formed by loading the bitumen with a suitable re-enforcement and distributing it over a metallic surface by centrifugal action, spraying, roll sleeking or the like.

For this purpose, I melt the bituminous material in a suitable vessel and add thereto. preferably with constant agitation, a certain percentage of sulphur, usually from 5% to 10% by weight of the bitumen but varying somewhat with the quality of bitumen.

The incorporation of the free sulphur with the molten bitumen sets up a very energetic reaction, with evolution of large quantities of gas containing both sulphur and hydrogen. The evolution of gas continues for a comparatively long time, usually several hours, and the mass should be kept molten until the evolution practically ceases.

The resulting product, when cooled, pos sesses the desired high melting point and toughness without brittleness. For example, a commercial bitumen containing initially six percent of combined sulphur and having a melting point of F., when treated by my process with six percent of free sulphur had its melting point raised to 130 F. and was much less brittle than other bitumens of similar melting point and hardness.

The mere presence of combined sulphur sometimes found in bitumens is ineffective to produce the desired result and heating and stirring of such sulphur bearing bitumen results in no noticeable evolution of sulphuretted hydrogen or any change of physical properties unless an appropriate percentage of free sulphur is added.

While the chemical changes occurring in my process have not been fully ascertained, it appears probable that the results obtained are due, at least in part, to the removal of hydrogen from one or more of the constituents of the bitumen, rather than to any comblnations entered into between the bitumen andadded sulphur, since most of the latter 1s given off as a gas or vapour during the treatment and little if any free sulphur remains in the treated product.

The bitumen is preferably mixed with a powdery reinforcing material, such as ground granite or siliceous material, in the proportions of about 30% bitumen and 70% relnforcing material. This admixture may take place during the sulphur treatment but is preferably subsequent thereto.

The coating is designed primarily for application to heated metallic surfaces and to metallic surfaces which have been primed by dipping in a liquid hydrocarbon at some time prior to coating. My improved coating may be applied by rolling or spraying, but when the surface to be coated is tubular, as in lining iron pipes, I prefer feeding the coating into the pipe at a temperature at Which the bitumen is fluid and rotating the pipe about its longitudinal axis at a speed sufficient to centrifugally spread the coating and force the reenforcing material toward the metal surface, the rotation being continued until the hydrocarbon has set. This produces a firmly adherent coating with a glossy uniform surface.

Having described my invention, I claim:

1. The improvement in the art of coating pipes or other articles which comprises intimately mixing with molten bitumen aproximately 5 to 10% of sulphur and a powdery re-enforcing material and spreading the product upon the surface of such pipe or article.

dery re-enforcing material, and spreading the product upon the surface of such pipe or article.

In testimony whereof I have hereunto set my hand this 11 day of May 1925.

BENJAMIN TALBOT. 

